Interfacial Chemistry of Self-etching Adhesive Bond after Prior Acid Etching

Self-etch and total etch adhesives are available for bonding composites to enamel and dentin, however neither is sufficient to ideally bond to both substrates.  Selective enamel etching has been suggested to improve self-etch adhesive’s bonding ability to enamel, but the effect of prior acid etching (total-etch) on dentin when using self-etch adhesives has not been studied.  Objectives: The purpose of this investigation was to study the effect of different self-etch adhesives on interfacial chemistry/morphology with dentin and enamel with and without prior acid etching.  Methods: Prepared paired teeth (n=12) were subjected to prior acid etching or no prior acid etching before either Scotchbond Universal or Easy Bond self-etch adhesives were applied on the surface.  Teeth were sectioned and examined using Raman microscopy and scanning electron microscopy.  Results:  Enamel with prior acid etching showed a significantly wider interface (5.14-5.22 um) than that (1.67-2.44 um) without prior acid etching (multivariate ANOVA with two-sided Mann-Whitney post hoc test, α=0.05). Raman results indicated that Easy Bond showed an inferior (gradient) penetration profile in dentin with prior acid etching, whereas Scotchbond Universal showed a better (less gradient) penetration profile.  SEM images clearly showed differences between both with and without prior acid etching samples and between the adhesives in dentin with prior acid etching.  Conclusions: The results suggest that Easy Bond does not penetrate well into etched dentin and that enamel without prior acid treatment shows no resin tags. Together, these suggest that selective enamel etching is extremely important when using Easy Bond adhesive, as Easy Bond bonds well with prior acid etched enamel but does not bond well with prior acid etched dentin.  Funded by UMKC SOD Summer Scholars Program.